Future: No oral polio vaccine in Nepal

Polio is a highly infectious disease, which is caused by a virus that invades the nervous system and causes paralysis. The virus is transmitted through person to person, mainly through the faecal-oral route.  Polio caused many deaths, morbidity and lifelong disability in the past and we can see traces of its fatal consequences as many deformed and paralyzed people in the villages of Nepal. However, the introduction of oral polio vaccine and its widespread coverage led to the reduction of its incidence and following fatal consequences. It is indeed a boon to mankind.

The Global Polio Eradication Initiative was launched in 1988. Since then oral polio vaccine has been used in the regular mass immunization. Oral Polio vaccines are available in different formulations.

OPV is available in different formulations:

·         Trivalent OPV – containing type 1, 2 and 3 serotypes

·         Bivalent OPV – containing type 1 and 3 serotypes

·         Monovalent OPV – containing one serotype (ie type 1, 2 or 3)

- See more at: http://www.polioeradication.org/Posteradication/OPVcessation.aspx#sthash.sC1ka2JW.dpuf

1.  Trivalent OPV: containing serotypes 1, 2, and 3
2.  Bivalent OPV: containing serotypes1, and 3
3.  Monovalent OPV: containing one serotypes (type1 or type 2 or type 3)

OPV is available in different formulations:

·         Trivalent OPV – containing type 1, 2 and 3 serotypes

·         Bivalent OPV – containing type 1 and 3 serotypes

·         Monovalent OPV – containing one serotype (ie type 1, 2 or 3)

- See more at: http://www.polioeradication.org/Posteradication/OPVcessation.aspx#sthash.sC1ka2JW.dpuf

OPV is available in different formulations:

·         Trivalent OPV – containing type 1, 2 and 3 serotypes

·         Bivalent OPV – containing type 1 and 3 serotypes

·         Monovalent OPV – containing one serotype (ie type 1, 2 or 3)

- See more at: http://www.polioeradication.org/Posteradication/OPVcessation.aspx#sthash.sC1ka2JW.dpuf

OPV is available in different formulations:

·         Trivalent OPV – containing type 1, 2 and 3 serotypes

·         Bivalent OPV – containing type 1 and 3 serotypes

·         Monovalent OPV – containing one serotype (ie type 1, 2 or 3)

- See more at: http://www.polioeradication.org/Posteradication/OPVcessation.aspx#sthash.sC1ka2JW.dpuf

OPV is available in different formulations:

·         Trivalent OPV – containing type 1, 2 and 3 serotypes

·         Bivalent OPV – containing type 1 and 3 serotypes

·         Monovalent OPV – containing one serotype (ie type 1, 2 or 3)

- See more at: http://www.polioeradication.org/Posteradication/OPVcessation.aspx#sthash.sC1ka2JW.dpufsome time line

There has been drastic improvement in the incidence of polio and paralysis and disability. There has been
Eradication of  Polio strain 2- 1999
Eradication of polio strain 3 - 2012

Inactivated polio vaccine (IPV) -since August 2014:
Inactivated polio vaccine was introduced on August 2014 in Nepal with the recommendation from National committee on Immunization Practices (NCIP). IPV is scheduled in 14 weeks of age after the birth of child until one year. IPV is produced from wild-type poliovirus strains of each serotype that have been inactivated (killed) with formalin. It is not a live vaccine and carries no risk of vaccine induced polio paralysis. The IPV induces low level of immunity in the intestine in comparison to oral polio vaccine and there is chance of multiplication of wild polio virus in the intestine and spread in the community. however, if the virus is contained in the community, there is less chance of contraction and furthermore spread making IPV effective. Though one dose IPV is given in Nepal as a complementary to current polio immunization, generally three spaced doses are administered to generate adequate levels of seroconversion, and most countries, a booster dose is added during late childhood.

IPV induces very low levels of immunity in the intestine. As a result, when a person immunized with IPV is infected with wild poliovirus, the virus can still multiply inside the intestines and be shed in the faeces, risking continued circulation.

Switch to bivalent oral polio vaccine containing polio strains 1 and 3 from trivalent oral polio vaccine polio strains 1,2 and 3 in Nepal on April, 2016:

This switch is in fact a major step to eradication of polio virus as this is required to eliminate the rare risks of vaccine-associated paralytic polio (VAPP) and circulating vaccine -derived poliovirus (cVDPV). This accords with one of the objectives of the Polio Eradication and Endgame Strategic Plan 2013-2018, which furthermore recommends removal of all oral polio vaccines in the long term.The removal of Polio strain2 is indeed required as this has been eradicated back in 1999 from the general population. This surely will help in eliminating vaccine induced type 2 polio in the immunized children.
Looking at this trend We are surely going to escape oral polio vaccine in the future.

Sources:

Bivalent oral polio vaccine (bOPV). Global Polio eradication Initiative. http://www.polioeradication.org/Polioandprevention/Thevaccines/BivalentOPV.aspx 

Replacing trivalent OPV with bivalent OPV: A critical step in polio eradication. Immunizations, vaccines and Biologicals. http://www.who.int/immunization/diseases/poliomyelitis/endgame_objective2/oral_polio_vaccine/en/ 

UNICEF, WHO, MOHP (Nepal). Introduction of Inactivated polio vaccine in Nepal: A public health milestone for polio free Nepal. December 2015. http://www.who.int/immunization/diseases/poliomyelitis/endgame_objective2/inactivated_polio_vaccine/Documentation_on_IPV_Introduction_in_Nepal_Final_lightversion.pdf